Audio amplifiers are used to process low-level sound signals to provide an output suitable for a speaker. There are a variety of sources for the low-level sound signals. For example, the low-level sound signals may be received from a radio receiver, an instrument pickup, a microphone, a record album, a magnetic tape, or a compact disc (CD). The low-level sound signal may not be of sufficient volume to be heard. The low-level sound signals may be input to the audio amplifier and the audio amplifier may process the signals to generate an output signal that is suitable for a speaker output. Audio amplifiers are used in most any application that requires driving a speaker.
Various criteria may be used to evaluate the performance of audio amplifiers. For example, an audio amplifier may be evaluated by frequency response, gain, and distortion. Distortion evaluates how closely the output signal tracks the input signal. Although distortion has some interesting applications, a system with high distortion cannot be said to be reproducing the input signal accurately. Sophisticated listeners may prefer a system with low distortion as the output more closely represents the input signal.